Front end loaders have been widely used in the handling of bulk materials and have been of increased capacity in recent years for greater efficiency and economy of operation. Various efforts have been made to increase the power and capacity of such loaders, as exemplified for instance by U.S. Pat. No. 3,363,792, issued Jan. 16, 1962. Said patent, owned by the assignee of this application, illustrates a front end loader designed for a bucket capacity on the order of 15 cubic yards, and which has enjoyed commercial success. However, efforts have continued to design an acceptable front end loader with a bucket capacity on the order of 18-24 cubic yards. While many parties have attempted such a design none, as yet, have met with commercial success for such reasons as initial cost, the requirement for special tires, lack of potential as a utility machine and lack of physical dimensions, such as dump height and reach, and bucket linkage to effectively load a 170 ton truck.
One of the problems that designers of 18-24 cubic yard loaders have not overcome is the enormous amount of hoisting energy that is lost when the bucket of a loader with a traditional bellcrank mechanism is dumped. In order to dump, the bucket must rotate forward from the rollback position to the full-dump position through an angle of nearly 130.degree.. This alone lowers the center of gravity of the load a substantial distance. The load then falls further out of the bucket and into the truck. As an example, in order to accommodate dumping, the load center of gravity must initially be raised 21 feet to somewhere above the truck. The load center of gravity then falls 11 feet into the truck, for a net elevation change of 10 feet. Approximately 50% of the hoisting energy used is lost. Clearly, reducing this energy loss would increase the productive capacity of a front end loader.
A mechanism that can substantially reduce the energy loss is an ejector assembly, placed in the bucket of the loader and used to move the contents of the bucket therefrom while the bucket remains in a raised, but horizontal position. Various ejector assemblies have been developed, but these have been inefficient due to operating characteristics and undue wear to material intrusion into the parts of the ejector assembly. Also there are advantages, in terms of reach and dump height, increased bucket capacity, cycle time, bucket breakout force and the like to be derived from the use of an ejector assembly in the bucket and the consequent horizontal dumping position. For instance, a bucket with an ejector assembly can place the last load in a truck with only a 25% loss in hoisting energy. Other advantages of the use of an ejector assembly, as compared to the traditional bucket geometry, include an increase in pile height up to 40% and reach up to 20%.